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in Vehicle tracking by
We are facing a problem with temperature sensors on an FMB120. We have install 4 dallas 18b20 sensors with resistance 4.7 ΚΩ  on a 50 meter distance. The problem is that the device looses the temperature sensors and sends 0 to the server. After 5 or 10 minutes it sends data again for 2 3 hours and then it sends 0. We test it on multible devices and also we replace the sensors but we are facing the same ishue.Also on the latest firware the device cannot read the data from dallas and gives a price 650000 when we downgrade it it works.

Please advice

Thank you in advance
Hi, do you solve this problem? I´m having same problem. We are working with FM3612 and 3 sensors (1mt each one, but we cut them), to 5mt, 15mt and 25mt. At our platform show 3000 as a value, and according Teltonika´s Manual, is a Dallas Error.

Do you contact Technical Support of Teltonika?


2 Answers

0 votes

FMB product's 1-Wire OUTPUT value is 3,8 V for 1-Wire devices, this limits the maximum distance of wire to be set for temperature sensors,  i suggest you testing your sensors, after connecting them with wire that is less than 10m in length to make sure the problem isn't with the distance of cable to the connected sensors. If the problem persists please respond me.

Sensor has been tested and they are working fine on a close range. The problem is the distance we have 50 meters of FTP cat6 and the sensors are failing to read by device. We are using 4k7 resistance between 1 wire power and 1 wire data as the manufactures of maxim states on the manual. The power voltage is 4.95 v at the end of the line so there is no power loss.

Best regards

I'm facing the same exact problem even though  sensors are tested on close range no problem, I have tried the to have one of the sensor longer Than the other  as the maximum distance 40 meter and checked the voltage there was no voltage drop and tried placing a steady voltage regulator receiving 12 v to 4 volts and it didn't work to as it interferes with the rest and drops them  devices test fmb 120 fmb630 and also 4200 and they work for 2 min then they go to zero please advice me.


0 votes
Hi to all

We had the same problem and also if you unplug the device and plug it again it will burn your sensors. This happens because when the device powers up it sends to one wire power for half a sec 12 or 24 v depending on the power supply.

Now for the sensors if you are using 4 dallas make sure the folowing:

1 use 24 volts power supply (beter than 12) minimum 5A

2 Make sure the device has valid GPS signal

3 Use a resistor 2.2 KΩ (not4.7)

This should solve your problem

Make sure that you will connect a capacitor 100 mf (paralel connection ) between one wire power and GND for protecting the thermometers.

If you still facing any problem please do not hesitate to contuct us in order to help you

Hope it helped
Capacitor 100uf ?
by anonymous
We are facing same problem with FMB130 and 1 wire temperature sensors, are there some official procedure or advice from Teltonika about these problems?